Checks if the value is not the type obtained from its object class equal to 'null' and not equal to null.

const isNotNull = <Type, Payload extends object = object>(
  value: Type,
  callback: ResultCallback<Type, Payload> = resultCallback,
  payload?: Payload
): value is Never<null, Type> =>
  callback(typeOf(value) !== 'null' && value !== null, value, payload);

Generic type variables


A generic type variable Type indicates the captured type of the given value via the return type value is Never<null, Type> and the value parameter of the provided callback function ResultCallback type.


The Payload generic type variable constrained by object indicates the type of optional parameter payload of the supplied callback function and payload optional parameter of the isNotNull() function from which it captures its value.


value: Type

The value of generic type variable Type, by default of the type captured from itself to check.

callback: ResultCallback<Type, Payload>

A callback function of ResultCallback type with parameters, the value that has been checked, the result of this check, and payload of generic type variable Payload with optional properties from the provided payload, to handle them before the result return. By default, it uses resultCallback() function.

payload?: Payload

An optional object of the generic type variable Payload is assigned to the payload of the given callback function.

Return type

value is Never<null, Type>

The return type is a boolean as the result of its statement indicating the value is a generic type Never that takes a generic type variable Type by default of value captured from the supplied value, but on the captured null changes to never.


The return value is a boolean indicating whether the provided value is not null.

Example usage

// Example usage.
import { isNotNull } from '@angular-package/type';

const anyNull: any = null;
const firstName = null;

isNotNull(anyNull); // return type is `value is any`
isNotNull(firstName); // return type is `value is never`

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